1. Field of the Invention
One aspect of the present invention relates to a method for measuring concentrations of gas moieties in a gas mixture.
2. Background Art
Many control systems rely on sensors to provide useful information regarding a concentration of a gas moiety in a gas mixture. Certain gas moieties may be suitable for determination of their concentrations by an electrochemical measurement. The electrochemical measurement may be acquired relatively simply and inexpensively by use of a gas sensor. However, some gas sensors may provide relatively slow output response signals to electrochemical changes in the gas mixture, or may exhibit a relative lack of sensitivity for a desired gas moiety. For example, the sensitivity may be diminished if the electrochemical changes of two chemical moieties are of opposite electrochemical sign. In certain cases, the opposite electrochemical signs may cancel each other, yielding a relatively low intensity net signal. In another example, the electrochemical response may be either augmented or diminished by an interfering gas moiety. For example, water vapor or oxygen may interfere with certain gas sensors.
Some sensors previously used methods focused on eliminating the interfering gas moiety. Examples of these methods include tuning the bias to be selective to only one analyte gas moiety; using catalysts to selectively react with the interfering gas moiety in order to yield a non-interfering gas moiety; as well as using an upstream filter or an electrochemical pump to physically remove the interfering gas moiety. Extra steps such as these may be incapable of removing all of the interfering gas moiety, and/or may modify the concentrations of the analyte gas moiety. In general, these methods add unacceptable costs to the method for measuring the concentration of the analyte gas moiety in the gas mixture.
In light of the foregoing, what is needed is a relatively inexpensive, but a relatively sensitive, method for measuring the concentration of the analyte gas moiety in the gas mixture. In addition, the method should be relatively insensitive to interfering gas moieties in the gas mixture without having to be selective for only one gas moiety.